SummaryThe roles of salicylic acid (SA) and H202 in the induction of PR proteins in tobacco have been examined. Studies were conducted on wild-type tobacco and plants engineered to express a bacterial salicylate hydroxylase capable of metabolizing SA to catechol (SH-L plants). Wildtype and PR-la-GUS-transformed plants express PR-la following challenge with Pseudomonas syringae pathovar syringae, SA or 2,6-dichloro-isonicotinic acid (INA). In contrast, SH-L plants failed to respond to SA but did express PR-la following INA treatment. H202 and the irreversible catalass inhibitor 3-amino-l,2,4-triazole (3-AT) were found to be weak inducers of PR-la expression (relative to SA) in wild-type tobacco but were unable to induce PR-la in SH-L plants, suggesting that the action of these compounds depends upon the accumulation of SA. A model has been proposed suggesting that SA binds to and inhibits a catalase inducing an increase in H202 leading to PR protein expression. Catalase activity has been measured in tobacco end no significant changes in activity following infection with P. syringae pv. syringee were detected. Furthermore, inhibition of catalass activity in vitro in plant extracts requires pre-incubation and only occurs at SA concentrations above 250 I~M. Leaf disks preincubated with I mM SA do accumulate SA to these levels and PR-la is efficiently induced but there is no apparent inhibition of catalass activity. It is also shown that a SAresponsive gene, PR-le, and a H202-sensitive gene, AoPR-1, are both relatively insensitive to 3-AT suggesting that induction of these genes is unlikely to be due entirely to inhibition of an endogenous catalase.

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SummaryThe role of salicylic acid (SA) in events occurring before cell death during the hypersensitive reaction (HR) was investigated in leaves of wild-type tobacco Samsun NN and in transgenic lines expressing salicylate hydroxylase (35S-SH-L). Challenge of 35S-SH-L tobacco with avirulent strains of Pseudomonas syringae gave rise to symptoms resembling those normally associated with a compatible response to virulent strains in terms of visible phenotype, kinetics of bacterial multiplication, and escape from the infection site. Compared with responses in wild-type tobacco, both the onset of plant cell death and the induction of an active oxygen species-responsive promoter (AoPR1-GUS) were delayed following challenge of 35S-SH-L plants with avirulent bacteria. The oxidative burst occurring after challenge with avirulent bacteria was visualized histochemically and quanti®ed in situ. H 2 O 2 accumulation at reaction sites was evident within 1 h after inoculation in wild-type tobacco, whereas in 35S-SH-L plants the onset of H 2 O 2 accumulation was delayed by 2±3 h. The delay in H 2 O 2 generation was correlated with a reduction in the transient rise in SA that usually occurred within 1±2 h following inoculation in wild-type plants. Our data indicate that an early transient rise in SA potentiates the oxidative burst, with resultant effects on accumulation of H 2 O 2 , plant cell death and also defence-gene induction, factors that together may determine the outcome of plant±pathogen interactions.

The purpose of this study was to develop an understanding of the current state of scientific data sharing that stakeholders could use to develop and implement effective data sharing strategies and policies. The study developed a conceptual model to describe the process of data sharing, and the drivers, barriers, and enablers that determine stakeholder engagement. The conceptual model was used as a framework to structure discussions and interviews with key members of all stakeholder groups. Analysis of data obtained from interviewees identified a number of themes that highlight key requirements for the development of a mature data sharing culture.

Abstract. The SOAP (Study of Open Access Publishing) project has analyzed the current supply and demand situation in the open access journal landscape. Starting from the Directory of Open Access Journals, several sources of data were considered, including journal websites and direct inquiries within the publishing industry to comprehensively map the present supply of online peer-reviewed OA journals. The demand for open access publishing is summarised, as assessed through a large-scale survey of researchers' opinions and attitudes. Some forty thousand answers were collected across disciplines and around the world, reflecting major support for the idea of open access, while highlighting drivers of and barriers to open access publishing.